Hello,
I have two lists, "Print Devices" and "Data Jacks", that each have a lookup column that points to the other. I'm doing this so that a user can start in either list and get additional information on the device configuration. This presents the problem of requiring extra steps to make changes, creating the risk that a user might not do both steps or could make a mistake leaving the lists out of sync.
What I want is for a change in one list to trigger an update in the other. The "Update Item" action won't work because you cannot enter dynamic data into the lookup field so I'm trying the HTTP request action. Here is the trigger:

And here is the HTTP request action:

I keep getting the error: "The parameter __metadata does not exist in method GetById."
I'm not very familiar with HTTP requests and have been using ChatGPT to assist but I'm just going around in circles with it. On one run, it partially worked but it created a new item instead of updating the existing one.
Any help would be appreciated!